DOHC engine moaning

[pr240sx]

MY 93 with 97,xxx miles makes a moaning sound whenever the engine is cold. have been making this sound since 45,xxx miles or so (basically like 8 years ago)

Stock engine, I have verified all pulleys and belts by starting the engine without any beltsOil pressure is ok as per FSM specs.Pilot bearing (car is manual) is okThe sounds seems to came from the front cover area, mid section

I have also removed the top timing chain guide and the upper low guide too as per Nissan specs. Noise still there. Other engines mods is the removal of the secondary butterflies.

Its changes pitch when I rev the engine, stops at 3000 rpms again engine cold. When I start the engine, is all quiet, then all of the sudden it start the moaning sound until warm up (15 to 20 mins after engine start)

changes oil from different synthetic weights (10W30, 5W30) to normal oil (20W50,10W30,10W40) noise still there, also tried several oil filters including Nissan factory one with no results

Any takers?

[Checkered-Member]

Oil pressure might be rising/dropping drastically while the car is cold.That will be my best guess

[Asleep Altima]

oil pressure wouldnt rise and drop when cold. it would rise because the oil is cold and thick. locate the area where the oil pump is and while the engine is running, stick a wooden dowel, like a broomstick or a long handled screwdriver to your ear. then place the other end on the part of the engine where the sound is coming from. i said oil pump to give you a place to start and because it wont be affected by the belts in any way. listen for the sound. do this until you find where the sound is at its loudest. lemme know what you find.

[pr240sx]

Just to let you knowthis is a DOHC engineThe oil pressure is constant at idleAlso, if was indeed oil pressure related, the engine could suffer from oil starvation and the seize after all this time?

Will try the home made stetoscope :> with all belts removed (they need to be changed anyways) Any consequences if I run the engine without the front crank pulley? (have to replace the seal also)

Will let you know my findings

Thanks!

[Asleep Altima]

Any consequences if I run the engine without the front crank pulley? (have to replace the seal also)

Will let you know my findings

Thanks!

yup, one minor, one major... the minor one is you wont have an alternator while the engine is running, the major one is, you wont have a water pump either... ive run my engine for a couple seconds at a time without the water pump to check my timing with a temporary pulley, but i dont suggest you do it while youre looking for a sound... keep the main belt attached and spray it with soapy water, it will keep the noise of the belt to a minimum while youre looking for that noise. good luck man.

[Altiman94]

Sounds like your having a time chain problem.

[pr240sx]

Preliminary findings!!

Using a long carboard tube I was able to locate (partially) from where the noise is, just behind the crank pulley!!!

Recap of the problemstarup moaning 'till engine is hot, when cold the noise is there up to 2500 rpms, then it stops.If I restart the car (engine cold) the noise will start again after a couple of seconds (10-15) then will go up to the engine is warm.

When the engine is warm the moaning just disappears, not even audible with the carboard tube against the lower part of the front cover!I can start the car several times, engine hot, and the noise is gone.Now will try this, warm up the engine 'till the moaning stops, drain the oil, add new cool (ambient temp) oil and restart.I am thinking that the moaning could be the regulator valve.Also, when I remove the oil filter, I should see the oil pressure relief valve and even touch it right? or its under the filter screw thingy assembly held by 4 screws?

:help

[ch1873857]

i had the same problem, its my clutch, it wasnt aligned

[pr240sx]

The sound is coming from the front cover, and if the clutch wasnt aligned it will vibrate, and I think that the sound be there all the time

Anyway thanks for the input

[ch1873857]

if your oil pressure IS low or someting, how can you regulate it?

[pr240sx]

By removing the oil regulator and stacking some washers in there to increase the pressure.Use a lower number oil

[pr240sx]

Today was cold and rainy afternoon here (cold at least for the tropic 7x degress)

The moaning was horrible, lasted the same but was awfully loud so it seems that its related to oil pressure or at least oil temperature

Really dont know what to do, use super light oil to "solve" or work around the problem or to change/inspect the oil pump (pain in the butt DOHC engine)

Could it be the oil regulator or bypass?Faulty drainback oil filter?

I am currently using 10w-40 on the engine, I used previously 10w-30 with no results.If I change to syntethic, lightweight syntethic (already tried 10w-30 syn oil, same results) maybe 5w-xx or something like that solve this?Keep in mind (regarding oil weights) that this is a tropical island and we have from 87 to 100 F in temperature range thru the year

[pr240sx]

Another update!

Changed my oil (3000 miles)with 10w-40 weight.Moaning was louder and lasted longer with new oil and oil filter, engine warm.SO I think that could be the engine weight/faulty regulator comboWill try using super low weight syntetic next time (maybe winter oil 0w30) and post my findings